Aerial and feeder system



Dec. 23, 1941. E c, CORK AL 2,267,446

AERIAL AND FEEDER SYSTEM Filed June 18, 1958 I To EDWARD 050/: c

ATTORNEY.

Patented Dec. 23, 1941 2,267,446 AERIAL AND FEEDER SYSTEM Edward CecilCork, Ealing, London, and Joseph Lade Pawsey, Hillingdon, England,assignors to Electric &' Musical Industries Limited, a British companyApplication June 18, 1938, Serial No. 214,437 In Great Britain June 23,1937 10 Claims. (01. 178- 44) v This invention relates to aerials andfeeder systems, and has particular reference to such systems in which anaerial is connected with a concentric feeder of the kind having one ormore conductors surrounded by an outer conducting sheath. The inventionis concerned with the suppression of undesired waves on the outside ofthe outer conducting sh'eath. In the specification of British Patent No.438,506, alternative methods of suppressing 'waves are described whichare applicable particularly to balanced aerials, the case of a centerfed dipole aerial being described in the specification. A feature commonto the methods described in the patent is the provision of an auxiliaryconductor one quarter of a wavelength long. and constituted by a wire orhollow conductor similar to the outer conducting sheath. The drawingsattach'edto the patent referred to show'an auxiliary conductor connectedto the aerial end'of the feeder and bent to lie parallel with thefeeder, one of the dipole conductors being connectedto the outerconducting sheath and the other dipole conductor being connected to thecentralv conductor and also to the auxiliary conductor. I Alternatively,one of the dipole. conductors is con:

nected directly to the central conductor and theother dipole conductoris connected to the outer sheath and auxiliary conductor. 1 In the caseof unbalanced aerial systems such,

for example, as a bottom fed dipole aerial, a

known method for reducing the effect of waves travelling up thefeederconsists in the provision of two quarter" wavelength conductorscon: nected to the outer sheath at the aerial end and extending onopposite sides of the feeder. The reduction-may be enhanced by theprovision of two further quarterwavelength conductors arranged at rightangles to the first pair, but spaced a distance such as one quarter of awavelength from the aerial end of the feeder. These quarter wavelengthconductors operateto reduce the impedance to earth from the points atwhich they are connected, to a value much lower than that of the aerial,and any wave travelling up, the feeder is. considerably attenuated.

The object of the present invention is to provide means for effectingfurther attenuation of undesired waves on the outside of the feeder thanis produced by the known methods outlined.

According to the presentinvention high frequency signalling apparatusincludes a main conductor providing a transmission path for signals andsubject to the transmission of-undesiredsignals along the outsidethereof attenuation for such undesired signals being introduced withoutsubstantially increasing the attenuation of desired signals, by anauxiliary conductor one end of which is connected to the end of saidmain conductor and the other end of which is connected to said mainconductor at a point which is at a given length from the end of saidmain conductor, said auxiliary conductor being of effective lengthincluding said given length and an additional length such that phasereversal of the. undesired signals occurs insaid auxiliary conductorwith resultant substantial cancellation thereof at the end of the saidmain conductor. In particular apparatus to which the invention isapplied, the auxiliary conductor is connected to a point in the mainconductor one quarter of a wavelength of the desired signal frequencyfrom the end of the main conductor. In an aerial and feeder system towhich the invention is applied, the length of the auxiliary conductorincludes a fraction of the order of one quarter of the wavelength of thedesired signal frequency and an additional length substantially equal toone half of said Wavelength. An auxiliary. conductor provided inaccordance withthe invention may be used in conjunction with a pair ofquarter Wavelength conductors extending on opposite sides of aconcentric feeder from the end of the feeder and a similar pair ofquarter wavelength conductors arranged at right angles to the first andconnected to the feeder at the point at which the auxiliary conductor isconnected thereto, The auxiliary conductor may be bent to lie in a planeon one side only of the concentric feeder or it may be bent to form azig-zag path having its axis constituted by the concentric feeder butshaped so as not to make contact with the feeder except at its end andat the point of connection.

In order that the invention may be more clearly understood and readilycarried into effect alternative conductor systems embodying theinvention will now be described by way of example and with reference tothe accompanying drawings in which:

Figures 1, 2 and 3 show three such alternative forms. 1

Referring to Figure 1 of the drawing, an aerial l is fed by a concentricfeeder 2 and at the end A of the feeder quarter wavelength conductors 3and 4 are connected to the feeder and extend on opposite sides as shown.At a point B distant by the length 1 from the end of the feeder, twofurther quarter wavelength conductors .5 and 6 are arranged atrightanglesto the conductors 3 and 4. Th'ese conductors operate toreduce the impedance from the points A and B to earth, so that any wavetravelling up the feeder 2 to the aerial is considerably attenuated.Actually these quarter wavelength conductors, together with the portionof the feeder between them, are equivalent to a band stop filterconsisting. of a tuned circuit with a shunt path to earth at each' end,the shunt paths each consisting of inductance and capacity in series.

A conductor '1 of length l+ \/2 is bent to the shape shown in Figure 1and connected at the points A and B, A being the operating wavelength.

The principle underlying the use of the additional length of feeder isthat waves passing up the feeder will divide at the point B and inconsequence of the extra half wavelength, the wave taking the path B, C,A will be in anti-phase at A to that going direct from B to A. Hencesuppression of the Wave will occur; An alternative method of regardingthe problem is to consider that the auxiliary conductor 1 forms with theoriginal conductor 2 a parallel tuned circuit so that there is a highimpedance between A and B. The two pairs of conductors 3, 4 and 5, 6 atthe points A and B provide additional attenuation.

It may be found that the presence of the additional conductor 1 givesrise to distortion of the directional diagram of the aerial, due to themutual coupling between the conductor 1 and the aerial. Such distortioncan largely be overcome by the provision of a conductor similar to theconductor 1 arranged on the opposite side of the feeder 2.

An alternative arrangement is shown in Figure 2 of the drawing in whichthe extra half wavelength of auxiliary conductor has been included bymaking the auxiliary conductor of zig-zag shape. It will be understoodthat the auxiliary conductor 1 in this case is connected to the mainconductor 2 only at the points A and B, sufficient space being leftbetween the auxiliary conductor and main conductor at the points atwhich they are in proximity to keep the capacity so introduced as low aspossible. The arrangement shown in Figure 2 has the effect of reducingthe mutual coupling between the auxiliary conductor I and the aerial sopreventing distortion of the directional'diagram of the aerial. Theconductors 3, 4 and 5, B are shown arranged in the same plane inFigure-2 instead of at right angles as in Figure 1. It is desirable thatthese conductors should be at a substantial angle to each other or toadjacent projecting conductors, but owing to the particular shape of theauxiliary conductor 1, it is preferable to arrange them in the sameplane instead of at right angles.

Fi ure 3 shows a further constructional form of an auxiliary conductorwhich is, in this case, arranged as a helix about the end of the feeder.The helix in this case has somewhat similar properties to the zig-zagconductor shown in Figure 2, but the conductors 3, 4 and 5, B arearranged at right angles to each other as in Figure 1.

While the expression Z+ \/2 has been used to indicate the length of theauxiliary conductor it is to be understood that the extra length of theauxiliary conductor beyond the length l is not necessarily an exactphysical half Wavelength in air, but may be modified by the dispositionof the conductor and its length may have to be adjusted experimentallyto produce the best cancellation of the waves it is desired to suppress.

The invention has been described in connection with a bottom fed aerial,but it will be understood that the invention may in general be appliedto the attenuation of waves along the outside of any high frequencyconductor. Thus, for example, it may be used in combination with any ofthe arrangements described in the specification of British Patent No.438,506 in order to provide very high attenuation of the wave travellingup the feeder to a center fed dipole aerial.

Having now particularly described and ascertained the nature of our saidinvention and in what manner the same is to be performed, we declarethat what we claim is:

1. High frequency signalling apparatus including a main conductorproviding a trans-mission path for signals and subject to thetransmission of undesired signals along the outside thereof, attenuationfor such undesired signals being introduced without substantiallyincreasing the attenuation of desired signals by an auxiliary conductorone end of which is connected to the end of said main conductor and theother end of which is connected to said main conductor at a point whichis at a given length from the end of said main conductor, said auxiliaryconductor being of effective length including said given length and anadditional length such that phase reversal of the undesired signalsoccurs in said auxiliary conductor with resultant substantialcancellation thereof at the end of said main conductor, and furtherconductors connected to said main conductor at each end of said givenlength to provide shunt paths to earth at each end of said given length,said length being such as to provide with said shunt paths a band stopfilter for said undesired signals.

2. High frequency signalling apparatus according to claim 1 wherein saidauxiliary conductor is connected to a point in said main conductor whichis of the order of one quarter of the wavelength of the desired signalfrequency from the end of said main conductor.

3. High frequency signalling apparatus including a main conductorproviding a transmission path for signals and subject to thetransmission of undesired signals along the outside thereof, attenuationfor such undesired signals being introduced Without substantiallyincreasing the attenuation of desired signals by an auxiliary conductorone end of which is connected to the end of said main conductor and theother end of which is connected to said main conductor at a point whichis at a distance equal to a quarter of the length of the operating wavefrom the end of said main conductor, said auxiliary conductor being ofan effective length including said quarter Wavelength and an additionallength equal to a half the length of the operating wave whereby phasereversal of the undesired signals occurs in such auxiliary conductorwith resultant substantial cancellation thereof at the end of said mainconductor, and further conductors connected to said main conductor at atleast one end of said quarter wave length portion to provide shunt pathsto earth for said undesired signals.

4. High frequency signalling apparatus including a main conductorproviding a transmission path for signals and subject to thetransmission of undesired signals along the outside thereof, attenuationfor such undesired signals being introduced without substantiallyincreasing the attenuation of desired signals by an auxiliary conductorone end of which is connected to the end of said main conductor and theother end of which is connected to said mainlconductor atla point whichis'at a distance equal to a'quarter of the length'ofthe operatingwave'from the end of said main conductor, said auxiliary conductor beingof an effective length including said quarter wavelength and anadditional length equal to a half the length of the operating wavewhereby phase reversal of: the undesired signals occurs in suchauxiliary conductor with resultant substantial cancellation. thereof atthe end of said main conductonand a pair of quarter wave conductorsextending perpendicularly on opposite sides of said main conductorateach point of connection of saidIaiixiIiarY 'cohductOr to said mainconductor.

5. High frequency signalling apparatus including a main conductorproviding a transmission path for signals and subject to thetransmission of undesired signals along the outside thereof, attenuationfor such undesired signals being introduced without substantiallyincreasing the attenuation of desired signals by an auxiliary conductorone end of which is connected to the end of said main conductor and theother end of which is connected to said main conductor at a point whichis at a distance equal to a quarter of the length of the operating wavefrom the end of said main conductor, said auxiliary conductor being ofan effective length including said quarter wavelength and an additionallength equal to a half the length of the operating wave whereby phasereversal of the undesired signals occurs in such auxiliary conductorwith resultant substantial cancellation thereof at the end of said mainconductor and a pair of quarter wave conductors extendingperpendicularly on opposite sides of said main conductor at each pointof connection of said auxiliary conductor to said main conductor, one ofsaid pairs of quarter wave conductors being in a plane at right anglesto the other of said pairs. I I

6. High frequency signalling apparatus including a main conductorproviding a transmission path for signals and subject to thetransmission of undesired signals along the outside thereof, attenuationfor such undesired signals being introduced without substantiallyincreasing the attenuation of desired signals by an auxiliary conductorone end of which is connected to the end of said main conductor and theother end of which is connected to said main conductor at a point whichis at a distance equal to a quarter of the length of the operating wavefrom the end of said main conductor, said auxiliary conductor being ofan effective length including said quarter wavelength and an additionallength equal to a half the length of the operating wave whereby phasereversal of the undesired signals occurs in such auxiliary conductorwith resultant substantial cancellation thereof at the end of said mainconductor and a pair of quarter wave conductors extendingperpendicularly on opposite sides of said main conductor at each pointof connection of said auxiliary conductor to said main conductor, one ofsaid pairs of quarter wave conductors being in a plane at right anglesto the other of said pairs, said auxiliary conductor being symmetricallydisposed with respect to said main conductor.

7. High frequency signalling apparatus including a concentric feederhaving an outer casing and inner conductor and providing a transmissionpath for signals and subject to the transmission of undesired signalsalong the outside thereof, attenuation for. such "undesired signalsbeing introduced without substantially increasingtheattenuation ofdesiredflsignals by an auxiliary conductor, one end of which isconnected to theend of saidcuter casingand the other end of whichis'connected 'to' said outer casing at a point which is at a lengthequal to a quarter of the length of-the operating wave from the end ofsaid outer casing, said auxiliary-conductor being of an eifective lengthincluding said quarter wavelength and an additional length equal to ahalf the length of the operating wave whereby phase reversal of theundesired signals occurs in said auxiliary conductor with resultantsubstantial cancellation thereof at the end of said outer casing, andfurther conductors connected to said main conductor at at least one endof said quarter wave length portion to provide shunt paths to earth forsaid undesired signals.

8. High frequency signalling apparatus including a concentric feederhaving an outer casing and inner conductor and providing a transmissionpath for signals and subject to the transmission of undesired signalsalong the outside thereof, attenuation for such undesired signals beingintroduced without substantially increasing the attenuation of desiredsignals by an auxiliary conductor, one end of which is connected to theend of said outer casing and the other end of which is connected to saidouter casing at a point which is at a length. equal to a quarter of thelength of the operating wave from the end of said outer casing, saidauxiliary conductor being of an effective length including said quarterwavelength and an additional length equal to a half the length of theoperating wave whereby phase reversal of the undesired signals occurs insaid auxiliary conductor with resultant substantial cancellation thereofat the end of said outer casing, and a pair of quarter Wave conductorsextending perpendicularly on opposite sides of said outer casing at eachpoint of connection of said auxiliary conductor to said outer casing.

9, High frequency signalling apparatus including a concentric feederhaving an outer casing and inner conductor and providing a transmissionpath for signals and subject to the transmission of undesired signalsalong the outside thereof, attenuation for such undesired signals beingintroduced without substantially increasing the attenuation of desiredsignals by an auxiliary conductor, one end of which is connected to theend of said outer casing and the other end of which is connected to saidouter casing at a point which is at a length equal to a quarter of thelength of the operating wave from the end of said outer casing, saidauxiliary conductor being of an effective length including said quarterwavelength and an additional length equal to a half the length of theoperating wave whereby phase reversal of the undesired signals occurs insaid auxiliary conductor with resultant substantial cancellation thereofat the end of said outer casing, and a pair of quarter wave conductorsextending perpendicularly on opposite sides of said outer casing at eachpoint of connection of said auxiliary conductor to said outer casing,one of said pairs of quarter wave conductors being disposed in a planeat right angles to the other of said pairs of conductors.

10. High frequency signalling apparatus including a concentric feederhaving an outer casing and inner conductor and providing a transmissionpath for signals and subject to the transmission of undesired signalsalong the outside thereof, attenuation for such undesired signals beingintroduced without substantially increasing the attenuation of desiredsignals by an auxiliary conductor, one end of which is connected to theend of said outer casing and the other end of which is connected to saidouter casing at a point which is at a length equal to a quarter of thelength of the operating wave from the end of said outer casing, saidauxiliary conductor being of an effective length including said quarterwavelength and an additional length equal to a half the length of theoperating wave whereby phase reversal of the undesired signals occurs insaid auxiliary conductor with resultant substantial cancellation thereofat the end of said outer casing, and a pair of quarter wave conductorsextending perpendicularly on opposite sides of said'outer casing at eachpoint of connection of said auxiliary conductor to said outer casing,one of said pairs of quarter wave conductors bein disposed in a plane atright angles to the other of said pairs of conductors, said auxiliaryconductor being coiled about said outer casing between its points ofconnection to said outer casing.

EDWARD CECIL CORK.

JOSEPH LADE PAWSEY.

